The systems of the body work together as a chain, for example: The muscles need the bones to have a shape, the muscles need the nervous system to feel when something is hurting or getting any problem and sending the signal to the brain, the muscles need the circulatory system cause the muscles work with blood.

As you can see all of the body systems work together. if one of them its not working it affects all of them eg: try to take out the circulatory system, all of the systems will stop working.